The present invention relates to a spray distribution measuring device for measuring the spray characteristic of a fuel injection nozzle used in a fuel injection device of an internal combustion engine and a method of measuring it.
The distribution of spray from a fuel injection nozzle used for an internal combustion engine greatly affects the performance of the internal combustion engine and waste therefrom. Several kinds of techniques have been adopted for the measurement.
FIGS. 9 and 10 show an example of conventional measuring devices and methods, respectively. FIG. 9 is a view showing the structure of a measuring device, and FIG. 10 is a view for explaining the measuring method. In FIGS. 9 and 10, reference numeral 1 denotes an injection nozzle which is an object for measurement. Reference numeral 2 denotes a nozzle driving circuit for driving the injection nozzle at any optional valve opening time, frequency and number of times of injection. Reference numeral 3 denotes a saucer installed at a prescribed port below the injection nozzle and partitioned to provide a plurality of regions each having a prescribed individual shape. Reference numeral 4 denotes a chamber with the injection nozzle attached to its upper surface and with the saucer 3 housed on the bottom, whose internal pressure is controllable.
In measuring the distribution of spray by the conventional measuring device thus structured, the nozzle driving circuit 2 drives the injection nozzle 1 at a prescribed valve opening time and number of times of injection. A spray test solution injected from the injection nozzle 1 becomes spray to fall into and trapped by each of the partitioned regions of the saucer 3. Upon completion of injection, the saucer 3 is taken out from the chamber 4. As seen from FIG. 10, the quantity trapped by each of regions of the saucer 3 is measured using a volume meter 5 such as a graduated cylinder. The chamber 4 is designed to improve the accuracy of test by separating the particulate spray test solution from the outer air flow and permit the test to be carried out under a positive pressure or negative pressure by changing the inner pressure as necessary.
In the measurement of the distribution of spray, in order to improve the measurement accuracy, it is necessary to increase the number of partitioned regions of the saucer 3 so that the area of each unit region is reduced. However, in the conventional measurement method as described above, an increase in the number of the partitioned regions leads to an increase in the time required for the measurement. Further, since the saucer 3 must be taken out from the chamber 4 for each measurement, in the measurement under the other condition than the atmospheric atmosphere, for each measurement, the internal pressure must be returned to the atmospheric pressure in order to open the chamber and at the subsequent measurement, the condition must be set again. This is very inefficient. In addition, when the test solution is replaced into the volume meter, an error is apt to occur so that the test accuracy may be deteriorated.
Further, in the SAE paper. 960108, another measuring technique is disclosed. This technique, with a large number of bottomed tubes, each of which has an opened upper end, arranged within the chamber, sprays a test solution from an injection nozzle from the top of the chamber, automatically measures a change in the weight of each bottomed tube using a plurality of load cells attached to an actuator and supplies the measured values to a computer for measurement of the distribution of spray. This technique could improve the measurement accuracy, but could not simultaneously carry out the measurement for all bottomed tubes arranged at a high density. Further, this technique, in which the actuator with the load cells attached is moved in three (X, Y and Z) directions in a predetermined order, was limited to shorten the measurement time. In addition, this technique, in which a large-scale actuator cannot be housed in the chamber, was required to open the chamber and reset the pressure for each measurement.